Circuit breaker with improved resettable latch and trip means

ABSTRACT

A circuit breaker comprises a stored-energy mechanism and an improved resettable roller-type latch means latching the storedenergy mechanism. The latch means is operable upon the occurrence of overload current conditions to release the stored-energy mechanism to thereby trip the breaker. The latch means may also be manually operated to trip the breaker.

United States Patent 1191 Maier 1 1451 Apr. 30, 1974 CIRCUIT BREAKERWITH IMPROVED RESETTABLE LATCH AND TRIP MEANS Alfred E. Maier, 128Dillon St, Beaver Falls, Pa. 15010 Filed: Jan. 30, 1973 Appl. No.:327,961

Inventor:

U.S. Cl. 335/167, 335/173 1111. c1. HOlh 73/02 Field of Search 335/167,168, 169, 170,

References Cited UNITED STATES PATENTS 6/1957 Frank .Q 335/191 Ill/II 13,460,075 8/1969 Yorgin et a] 335/9 Primary Examiner-Harold BroomeAttorney, Agent, or FirmW. A. Elchik ABSTRACT A circuit breakercomprises a stored-energy mechanism and an improved resettableroller-type latch means latching the stored-energy mechanism. The latchmeans is operable upon the occurrence of overload current conditions torelease the stored-energy mechanism to thereby-trip the breaker. Thelatch means may also be manually operated to trip the breaker.

10 Claims, 4 Drawing Figures PATENTEBAPR 30 \974 3808.567

SHEET 2 0F 3 PATENTEB APR 3 0 i974 SHEET 3 OF 3 CIRCUIT BREAKER WITHIMPROVED RESETTABLE LATCH AND TRIP MEANS CROSS-REFERENCE TO RELATEDAPPLICA- TIONS Cross-reference is herein made to the copendingapplications of Alfred E. Maier et al. Ser. No. 327,964; Alfred E. Maieret al. Ser. No. 327,972; and Alan B. Shimp Ser. No. 327,973all of whichapplications are filed concurrently herewith.

BACKGROUND OF THE INVENTION 1. Field of the Invention Circuit breakers,and more particularly circuit breakers of the type comprising a latchedstored-energy mechanism releasable to effect tripping operations.

2. Description of the Prior Art A circuit breaker having an operatingmechanism of the type herein disclosed is disclosed in the patent toCellerini, US. Pat. No. 3,662,134. A circuit breaker comprising astored-energy mechanism latched by means of a latch structure thatincludesa roller latch is disclosed in the patent to Nick Yorgin et al.,US. Pat. No. 3,460,075. The latch structure of the subject invention isan improvement over the above-mentioned prior art in that first andsecond'roller means are utilized in order to provide a force reductionthrough the latch structure with reduced friction.

SUMMARY OF THE INVENTION A circuit breaker comprises a pair of contactsand a stored-energy mechanism releasable to trip open the contacts.Improved roller-type latch means is provided for latching thestored-energy mechanism. The latch means comprises a first latch membersupported for pivotal movement about one end thereof and carrying afirst roller means in proximity to the other end thereof. The firstroller means engages a releasable member of the stored-energy mechanismto latch the stored-energy mechanism. The latch means comprises a secondpivotally supported latch member. A second roller means is providedbetween the second and first latch members in proximity to said otherend of the first latch member to provide a latching engagement betweenthe second and first latch members. The first and second roller means onthe first and second latch members enables a force reduction through thelatch structure with reduced friction. A third latch member is providedfor latching the second latch member, and means is operable to move thethird latch member to an unlatching position to thereby release thefirst and second latch members to thereby release the releasable memberwhereupon the stored-energy mechanism is automatically operated to thetripped open position. The third latch member cooperates with anexternally accessible manually operable member. An operator can depressthe manually operable member to move the third latch member in order toprovide a manual .tripping operation. The first and second roller meansmore specifically comprise a first roller supported on and between apair of opposite legs of the first latch member and a pair of secondrollers supported on the first latch member on the outer sides of theopposite legs of the first latch member. The second rollers engage apair of spaced latch surfaces on a pair of spaced leg portions of thesecond latch member when the latch structure is in the latched position.The stored-energy of the operating mechanism provides the driving forcefor moving the releasable member which operates through the rollerlatches to move the first and second latch members out of the latchingposition when the third latch member is moved to unlatch the latchstructure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view, withparts broken away, through the center pole unit of a three-pole circuitbreaker;

FIG. 2 is a side view with parts broken away illustrating part of thelatch-and-trip means disclosed in FIG.

FIG. 3' is a top plan view, with the releasable trip member broken away,of the latch-and-trip means seen in FIG. 2; and

FIG. 4 is a section view of the structure shown in FIG. 3 with otherparts of the breaker added and with the latch structure shown in thetripped position.

DESCRIPTION OF THE PREFERRED.

EMBODIMENT Referring to the drawings, there is shown, in FIG. 1, thecenter pole unit of a three-pole molded-case or insulating-housing typecircuit breaker 5. The trip means of the circuit breaker 5 is morespecifically described in the above-mentioned patent application ofAlfred E. Maier et a] Ser. No. 327,972. The circuit breaker-5 comprisesan insulating housing comprising a molded insulating base 11 and amolded insulated cover 13.

Suitable insulating barrier means separates the housing l1, 13 intothree adjacent insulating compartments for housing the three pole unitsof the three-pole circuit breaker in a manner well-known in the art. Ineach pole unit, two terminals 15 and 17 are provided at openings in thebase 11 in proximity to the opposite ends of the housing to enableconnection of the circuit breaker in an electric circuit.

In each of the three pole-unit compartments of the circuit breaker,there are two spaced conductors 21 and 23 suitably secured to the base11. The terminal 15 is secured to the flat under surface of theconductor 21. A stationary contact 25 is fixedly secured to the front ofthe conductor 21. A rigid main conductor 27 is mounted on the base 11and connected, at one end thereof, to the conductor 23. The otherterminal 17 is connected to the flat under surface of the conductor 27.

A single stored-energy type operating mechanism 29, for controlling allthree pole units, is mounted in the center pole unit compartment of thecircuit breaker. In addition to the stationary contact 25, there is astationary contact 31 mounted on the conductor 21 and a stationarycontact surface 33 on the conductor 23 in each pole unit of thecircuitbreaker. The operating mechanism 29 is operable to move a movablecontact structure indicated generally at 35 between open and closedpositions. The movable contact structure 35 is of the type morespecifically described in the patent to Cellerini, US. Pat. No.3,662,134. The movable contact structure 35 comprises a plurality ofmain bridging contact arms 37 and an arcing contact arm 39. Each of themain bridging contact arms 37 comprises a contact surface 41 cooperablewith the stationary contact surface 33 and a contact 43 cooperable withthe contact 31, and the arcing contact arm 39 comprises a contact 45cooperable with the stationary contact 25. The contact structure 35 issupported on a contact carrier 47 that is supported for pivotal movementabout a pivot pin 49. rigid insulating tie bar 51 extends across allthree pole units and is connected to the three contact carriers 47 tosimultaneously move the three contact carriers 47 between open andclosed positions. The contact carrier 47, for the center pole unit, ispivotally connected to a lower toggle link 53 by means of a pivot pin55. The lower toggle link 53 is pivotally connected to an upper togglelink 57 by means of a knee pivot pin 59. The upper toggle link 57 ispivotally connected to a releasable trip member 61 by means of a pivotpin 63. The releasable trip member 61 is supported at one end thereoffor pivotal movement about a fixed pivot pin 65. The releasable tripmember 61 is latched, at the other end thereof, by means of a latchstructure 67 An inverted generally U-shaped operating lever 69 issupported at the inner ends of the legs thereof for pivotal movement ona pair of fixed pins 71. Tension springs 73 are connected at the lowerends thereof to the knee pivot 59 and at the upper ends thereof to thebight portion of the operating lever 69. A handle structure 75 isconnected to the front end of the operating lever 69 and comprises ahandle part 77 that extends out I through an opening 79 in the front ofthe cover 13. The handle structure 75 comprises a shroud 81 thatsubstantially closes the opening 79 in all positions of the handlestructure 75. In each pole unit, an arcextinguishing structure 85,comprises a plurality of generally U-shaped magnetic plates87 supportedin a spaced stacked relationship. The arc-extinguishing structure 85operates to extinguish arcs drawn between the contacts 25, 45 duringopening operations in a manner well-known in the art.

In each pole unit, the arcing contact arm 39 is electrically connectedto the conductor 23 by means of a flexible conductor 89. In the closedposition of the contacts, the circuit, through each pole unit, extendsfrom the terminal 17 through the conductor 27, the conductor 23, themovable contact structure 35, the

conductor 21, to the other terminal 15. The main bridging contact arms37 carry most of the current in the closed position of the contacts, andthe current path through these contact arms extend from the contactsurfaces 33, through the contacts 41, the bridging contactm embers 37-,the contacts 43, to the contact 31. During opening operations, the mainbridging contacts 43, 31 separate first and thereafter, the current iscarried from the conductor 23 through the flexible conductor 89, thearcing contact arm 39, the arcing contact and the arcing contact 25.When the arcing contact arm 39 separates an arc is drawn between thecontacts 25, 45 and extinguished in the arcextinguishing structure 85 ina manner well known in the art. 7

The circuit breaker is shown in FIG. 1 in the open position with thereleasable trip member 61 latched in the latched position shown by meansof the latch mechanism 67. In order to close the circuit breaker, thehanunit in a clockwise direction about the pivot 49 to the closedposition. With the three contact carriers 47 being connected forsimultaneous movement by means of the tie bar 51, this movement servesto simultaneously move all three of the movable contact structures tothe closed position. When it is desired to manually open the circuitbreaker, the handle 77 is moved counterclockwise to the off positionseen in FIG. 1. This moves the springs 73 overcenter to cause collapseof the toggle 53, 57 to thereby move the contact structures 35 to theopen position illustrated in FIG. 1. Each of the contact carriers 47 andmovablecontact struc' tures 35 moves about the associated pivot pin 49-with all of the contact carriers and movable contact structures movingabout a common axis between the open and closed positions.

When the circuit breaker is in the closed position and an overloadoccurs in any of the three pole-units, the releasable member 61 will bereleased, in a manner to be hereinafter described, to automatically tripthe circuit breaker open. Upon release of the releasable member 61,thesprings 73, which are in a charged condition, rotate the trip member61 in a clockwise'direction about the pivot to cause collapse of thetoggle 53, 57 to thereby move the three contact carriers 47 and movablecontact structures 35 to the open position in a manner well known in theart. Upon tripping movement of the circuit breaker, the handle 77 ismoved to an intermediate position in between the off and on positions toprovide a visual indication that the circuit breaker has tripped open.

Following a tripping operation, it is necessary to reset and relatch thecircuit breaker mechanism before the contacts can be closed. Resettingand relatching is achieved by moving the handle 77 to a position pastthe off position.- During this movement, a pin member 91 on thereleasable member 61 engages a shoulder portion 93 on the releasablemember 61, and the releasable member 61 is moved down to a position torelatch the latch structure 67 in a manner to be hereinafter described.Following relatching of the latch structure 67, when the operatorreleases the handle 77 the releasable member 61 will again be reset andrelatched in the position seen in FIG. 1. Thereafter, the circuitbreaker can be operated in the same manner as was hereinbeforedescribed.

Referring to FIGS. 1 and 2-4, the latch structure 67 comprises agenerally U-shaped support bracket 97 that is secured to the conductor27 of the center pole unit and to the base 11 by means of a pair of.bolts 99. A first latch member indicated generally at 101 is mountedfor pivotal movement on a pivot pin 103 that is secured between theopposite side plates of the support bracket 97. As can be understoodwith reference to FIGS. 2-4, the first latch member 101 comprises a pairof spaced leg parts 105 and a bight part 107 connecting the spaced legparts 105. A first roller 109 is supported between the leg parts 105 ona pin 111 that is secured to the spaced leg parts 105. A pair of secondrollers 113 are also supported on the pin 111 on the outer sides of thespaced leg parts 105 (FIG. 3). A torsion spring 115 biases the firstlatch member 101 in a counterclockwise (FIGS. 2 and 4) direction aboutthe pivot pin 103. The latch structure 67 also comprises a second latchmember indicated generally at 117. The second latch member 117 comprisesa pair of spaced leg parts 119 and an intermediate or bight part 121that connects the opposite spaced leg parts 119 (FIGS. 3 and 4). A pairof spaced pins 123 (FIGS. 2-4) are secured to the side plates of thesupporting frame 97, and

the spaced legs 119 are pivotally supported on the pins 123 to supportthe second latch member 117 for pivotal movement on the pins 123. Theopposite legs 119 of the latch member 117 are provided with notches 127therein for receiving the rollers 113 in a manner to be hereinafterdescribed. The latch structure 67 also comprises a third latch member,indicated generally at 131, that latches the second latch member 117 inthe latched position seen in FIGS. 13. The third latch member 131comprises a downwardly extending leg 133, having a window opening 135(FIG. 4) therein, and a generally horizontal leg 137. The latch member131 is supported on a support plate 139 for pivotal movement about anaxis normal to the plane of the paper as seen in FIG. 4 and indicatedgenerally at 141. As can be understood with reference to FIGS. 2-4, theconnecting part 121 of the second latch member 117 has a smallprojecting part 145 (FIG. 3) that rests on a ledge in the window opening135 (FIG. 4) to latch the second latch member in the latched positionseen in FIGS. 13.

The latch structure 67 is automatically unlatched upon the occurrence ofoverload current conditions by means of a magnetic trip actuatorindicated generally at 147. The magnetic trip actuator 147 is morespecifically described in the above-mentioned copending patentapplication of Alfred E. Maier et al. .Ser. No. 327,964 filed .I an. 30,1973. The magnetic trip actuator 147 comprises an armature plunger 148that is maintained in the inoperative position shown in FIG. 2 bymagnetic means and spring biased towards an extended or actuatingposition (FIG. 4) by means of a spring 149. The plunger 148 comprises ashoulder part 150 and an extension 151 that extends through an opening152 in the latch member 131 during tripping operations. A static circuitboard indicated generally at 153 (FIG. 1) is supported near the front ofthe breaker. The static circuit board 153 supports the components of astatic trip circuit that is more specifically described in theabove-mentioned copending patent application of Alan B. Shimp Ser. No.327,973. In each pole unit, a first current transformer indicatedgenerally at 155 (FIG. 1) is supported around the associated conductor27. Upon the occurrence of an overload in any of the pole units, thetransformer 155 senses the overload and energizes a second transformer(not shown) to operate through the static circuit 153 to pulse themagnetic trip actuator 147 to thereby release the front armature plunger149 whereupon the spring 149 moves the armature plunger 148 from theinitial position seen in FIGS. 1 and 2 to the extended actuatingposition seen in FIG. 4. This operation is more specifically describedin the abovementioned patent applications Ser. No. 327,964 Ser. No.327,972 Ser. No. 327,973.

Upon movement of the armature plunger 148 to the extended actuating ortripping position seen in FIG. 4, the shoulder part 150 engages andpivots the third latch member 131 in a counterclockwise direction aboutthe pivot 141 to effect a tripping operation of the circuit breaker in amanner to be hereinafter described.

The circuit breaker is shown in FIGS. 1-3 with the releasable member 61in the latched position. In this position of the releasable member 61,when the circuit breaker contacts are in the closed position, the toggle53, 57 is erected and the springs 73 are in a charged condition biasingthe toggle 53, 57 toward a collapsed position. In this position, thecharged springs 73 bias the upper toggle link 57 to bias the releasablemember 61 in a clockwise direction about the pivot 65. This movement isprevented by the engagement of the free end of the relesable member 61engaging the latch roller 109 and biasing the first latch member 101 ina counterclockwise direction about the pivot 103. This movement islimited by the engagement of the latch rollers 113 (FIGS. 2 and 3) withthe spaced ann portions of the second latch member 117, with the rollers113 being disposed in the slots 127 of the spaced leg portions of thesecond latch member 117. The force of the operating springs 73,operating through the first latch member 101 and the second latch member117, biases the second latch member in a counterclockwise directionabout the pivot 123. Counterclockwise movement of the second latchmember 117 is prevented by the engagement of the latch projection (FIG.3) with the ledge in the window opening 135 (FIG. 4) of the third latchmember 131 so that with the parts in the position seen in FIGS. 1-3, thestored energy operating mechanism is latched and will remain latcheduntil the releasable member 61 is released.

Upon movement of the plunger 148 to the extended actuating or trippingposition seen in FIG. 4, the circuit breaker is tripped. During thismovement, the shoulder 150 of the plunger 148, operating against thethird latch member 131, pivots the third latch member 131 in acounterclockwise direction about the pivot 141 whereupon the windowlatch 135 of the third latch member 131 releases the projection 145(FIG. 3) to thereby release the second latch member 117. Upon release ofthe secondlatch member 117, the springs 73 (FIG. 1) move the releasablemember 61 in a clockwise direction about the pivot 65 (FIG. 1). Thismovement of the releasable member 61 operates through the first rollermember 109 and second roller members 113 to move the first latch member101 counterclockwise and to move the second latch member 117counterclockwise to the unlatched tripped open position seen in FIG. 4.During this movement the releasable member 61 moves to the trippedposition to effect collapse of the toggle 53, 57 to trip the circuitbreaker in the manner hereinbefore described.

The circuit breaker 5 comprises a novel latch struc ture withsubstantial force reduction through a pair of latches that providelatching through two sets of roller means to enable a relativelylow-force and positive trip operation.

The latch structure 67 and releasable member 61 are shown in thetripped-open position in FIG. 4. In order to reset the circuit breaker,the releasable member 61 is moved counterclockwise by movement of thehandle 77 to a resetting position past the full off position of thehandle 77 in the manner that was hereinbefore described. During thismovement, the free end of the releasable member 61 engages the bightportion 107 of the first latch member 101 to pivot the first latchmember 101 in a clockwise direction about the pivot 103. Near the end ofthis movement, the two rollers 113 drop into the notches 127 of thesecond latch member 117 and a torsion spring 158 moves the second latchmember 117 in a clockwise direction about the pivot 123 to the latchedposition in FIG. 2. During this movement, the insulating shroud portion81 (FIG. 1), of the operating handle structure 75, engages one arm 163of a member 165. The member 165 is generally T-shaped in side view. Themember 165 comprises a pair of arms 167 extending horizontally to theleft (FIGS. 2 and 4), the arm 163 extending horizontally to the rightand a downwardly extending leg 169. The arms 167 are pivotally supportedon the plate 139 to support the member 165 for pivotal movement about anaxis 141 (FIG. 4) that is generally normal to the plane of thepaper asseen in FIG. 4. During resetting movement of the handle structure 75 theshroud 81 pivots the member 165 in a clockwise (FIG. 4) direction, andthe downwardly extending leg 169, engaging the projecting part 151 ofthe plunger 148 moves the plunger 148 against the bias of the spring 151back to the reset and relatched position seen in FIGS. 1-3. As theplunger 148 is moved back to the reset position, a spring 160 (FIG. 4)operating on the member 131, biases the member 131 in a clockwisedirection about the pivot 141 to the reset position seen in FIGS. l-3wherein the extended projecting latch portion 145 (FIG. 3) of the secondlatch member 117 is again latched in the window opening 135 of the thirdlatch member 131. As can be understood with reference to FIG. 1, whenthe handle structure 75 is moved to reset and relatch the breaker, thehandle structure is moved close to the limit of movement in the opening79, and upon release of the handle structure 75 following a resettingand relatching operation the springs 73 will return the handle structure75 a short distance to the position seen in FIG. I. When the armatureplunger 148 reaches the reset position seen in FIGS. 1-3, the magnetictrip actuator will automatically reset and the armature structure 148will be maintained-in the reset position by permanent mag netic means ina manner described in the abovementioned application of Alfred E. Maieret al. Ser. No. 327,964.

Referring to FIG. 3, it will be noted that the arm 137 of the thirdlatch member 131 has an opening 173 therein. A pin member 175 (FIGS. 1and 4) is provided with a lower portion that extends through the openingin the arm 137 and an upper portion that engages an adjustable screw 177that is screwed into the lower end of a push-button member 179 that ispositioned in an opening 181 in the insulating cover 13. The spring 160biases the third latch member 131 in a clockwise direction to thelatched position and biases the member 175 upward to thereby bias thepush-button member 179 to the upper unactuated position seen in FIG. 1.When the circuit breaker is in the closed position and it is desired tomanually trip the circuit breaker, the push-button 179 is presseddownwardly against the bias of the spring 160 to move the third latchmember 131 in a counterclockwise direction to the tripped position torelease the latched structure 67 and the releasable member 61 to therebytrip the circuit breaker in the same manner as was hereinbeforedescribed. During the manual push-to-trip operation the armature plunger148 remains in the initial unactuated position seen in FIGS. 1 and 2.Following a manual push-to-trip operation the circuit breaker isrelatched in the same manner as was hereinbefore described by movementof the handle structure 75 to the resetting position.

I claim:

- I. A circuit breaker comprising a pair of contacts, a latchedreleasable member releasable to effect opening of said contacts, latchmeans latching said releasable member, said latch means comprising afirst latch member, first pivot support means in proximity to one end ofsaid first latch member supporting said first latch member for pivotalmovement, a first roller means on one of said releasable and first latchmembers, said first roller means being positioned in proximity to theother end of said first latch member, said first roller means latchingsaid releasable member, a second latch member, a second pivot supportmeans supporting said latch member for pivotal movement, a second rollermeans on one of said first and second latch members latching said firstlatch member in proximity to said other end of said first latch member,and means operable to release said second latch member whereupon saidsecond latch member releases said first latch member to thereby releasesaid releasable member.

2. A circuit breaker according to claim 1, and said first roller meanscomprising a roller member supported on said first latch member inproximity to said other end of said first latch member.

3. A circuit breaker according to claim 2, and said second roller meansbeing supported on said first latch member in proximity to said otherend of said first latch memberv 4. A circuit breaker according to claim3, said first latch member comprising a pair of spaced arm portions,said first roller member being supported on said spaced arm portionsbetween said spaced arm portions, said second roller means comprising apair of second rollers supported on the outer sides of said spaced armportions, and said second latch member comprising a pair of spaced armportions engaging said second rollers to latch said first latch memberin the latched position.

5. A circuit breaker according to claim l, a third latch member in alatching position engaging said second latch member to latch said secondlatch member, said third latch member being operable to an unlatchingposition, upon movement of said third latch member to the unlatchingposition said third latch member releasing said second latch member torelease said first latch member to thereby release said releasablemember, and means operable upon the occurrence of overload currentconditions above a predetermined value to automatically move said thirdlatch member to the unlatching position.

6. A circuit breaker according to claim 5, said circuit breakercomprising aninsulating housing, and-manually accessible meansaccessible from outside of said insulating housing and being manuallyoperable to move said third latch member to said unlatching position.

7. A circuit breaker according to claim 2, a third I latch member in alatching position engaging said second latch member to latch said secondlatch member, said third latch member being movable to an unlatchingposition, upon movement of said third latch member to the unlatchingposition said third latch member releasing said second latch member torelease said first latch member to thereby release said releasablemember, and means operable upon the occurrence of overload currentconditions above a predetermined value to automatically move said, thirdlatch member to an unlatching position.

8. A circuit breaker according to claim 7, said circuit breakercomprising an insulating housing, said insulating housing having anopening therein, a manually operable member accessible at sais opening,and said manually operable member being manually operable to move saidthird latch member to said unlatching posi- I tion.

9. A circuit breaker according to claim 3, a third latch member in alatching position engaging said second latch member to latch said secondlatch member, said third latch member being movable to an unlatchingposition to release said second latch member to thereby release saidfirst latch member to thereby release said releasable member, and meansoperable third latch member to said unlatching position.

1. A circuit breaker comprising a pair of contacts, a latched releasablemember releasable to effect opening of said contacts, latch meanslatching said releasable member, said latch means comprising a firstlatch member, first pivot support means in proximity to one end of saidfirst latch member supporting said first latch member for pivotalmovement, a first roller means on one of said releasable and first latchmembers, said first roller means being positioned in proximity to theother end of said first latch member, said first roller means latchingsaid releasable member, a second latch member, a second pivot supportmeans supporting said latch member for pivotal movement, a second rollermeans on one of said first and second latch members latching said firstlatch member in proximity to said other end of said first latch member,and means operable to release said second latch member whereupon saidsecond latch member releases said first latch member to thereby releasesaid releasable member.
 2. A circuit breaker according to claim 1, andsaid first roller means comprising a roller member supported on saidfirst latch member in proximity to said other end of said first latchmember.
 3. A circuit breaker according to claim 2, and said secondroller means being supported on said first latch member in proximity tosaid other end of said first latch member.
 4. A circuit breakeraccording to claim 3, said first latch member comprising a pair ofspaced arm portions, said first roller member being supported on saidspaced arm portions between said spaced arm portions, said second rollermeans comprising a pair of second rollers supported on the outer sidesof said spaced arm portions, and said second latch member comprising apair of spaced arm portions engaging said second rollers to latch saidfirst latch member in the latched position.
 5. A circuit breakeraccording to claim 1, a third latch member in a latching positionengaging said second latch member to latch said second latch member,said third latch member being operable to an unlatching position, uponmovement of said third latch member to the unlatching position saidthird latch member releasing said second latch member to release saidfirst latch member to thereby release said releasable member, and meansoperable upon the occurrence of overload current conditions above apredetermined value to automatically move said third latch member to theunlatching position.
 6. A circuit breaker according to claim 5, saidcircuit breaker comprising an insulating housing, and manuallyaccessible means accessible from outside of said insulating housing andbeing manually operable to move said third latch member to saidunlatching position.
 7. A circuit breaker according to claim 2, a thirdlatch member in a latching position engaging said second latch member tolatch said second latch member, said third latch member being movable toan unlatching position, upon movement of said third latch member to theunlatching position said third latch member releasing said second latchmember to release said first latch member to thereby release saidreleasable member, and means operable upon the occurrence of overloadcurrent conditions above a predetermined value to automatically movesaid third latch member To an unlatching position.
 8. A circuit breakeraccording to claim 7, said circuit breaker comprising an insulatinghousing, said insulating housing having an opening therein, a manuallyoperable member accessible at sais opening, and said manually operablemember being manually operable to move said third latch member to saidunlatching position.
 9. A circuit breaker according to claim 3, a thirdlatch member in a latching position engaging said second latch member tolatch said second latch member, said third latch member being movable toan unlatching position to release said second latch member to therebyrelease said first latch member to thereby release said releasablemember, and means operable upon the occurrence of overload currentconditions above the predetermined value to automatically move saidthird latch member to said unlatching position.
 10. A circuit breakeraccording to claim 9, said circuit breaker comprising an insulatinghousing, and manually operable means accessible from outside of saidhousing and being manually operable to move said third latch member tosaid unlatching position.